Amino Acid Residues within Enterohemorrhagic<i>Escherichia coli</i>O157:H7 Tir Involved in Phosphorylation, α-Actinin Recruitment, and Nck-Independent Pedestal Formation
Bibliographic record
Abstract
Enterohemorrhagic Escherichia coli (EHEC) O157:H7 and enteropathogenic E. coli (EPEC) adherence to epithelial cells results in the formation of actin pedestals. Pedestal formation requires the bacterial protein Tir, which is inserted into the epithelial cell plasma membrane by the type III secretion system. EPEC and EHEC use different Tir-based mechanisms for pedestal formation, and the EPEC Tir residues required have been well described. In contrast, little is known about the regions of EHEC O157:H7 Tir that are essential for pedestal formation. Additionally, EHEC O157:H7 Tir is serine/threonine phosphorylated, although the residues involved and their role in pedestal formation are not known. In this study, we describe two regions within the carboxy terminus of EHEC O157:H7 Tir that are required for phosphorylation and pedestal formation. Serines 436 and 437 are substrates for protein kinase A phosphorylation, although this is not required to form pedestals. Using a series of internal deletion mutants, we found that amino acids 454 to 463 are required for efficient pedestal formation. Deleting this region resulted in a significant decrease in the recruitment of both filamentous actin and the actin binding protein alpha-actinin. As alpha-actinin binds directly to the EHEC O157:H7 amino terminus, these data suggest that its recruitment is dependent on pedestal formation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".